Lubricating composition



Patented Dec. 18, 1945 v LUBRIQATING COMPOSITION William Helmore, Kingston Hill, England, as-

signor to O. C. Wakefield & Company Limited, Beaconsfield, England, a British company No Drawing. Application June 23, 1942, Serial No. 448,153. In Great Britain April '4, 1941 4 Claims. (01. 252-372) This invention is for improvements in or relating to lubricating compositions, especially lubricating compositions that are to be employed in internal-combustion engines, i. e. under conditions which tend to disrupt the lubricating oil- During recent years, a large variety of different substances have been suggested for incorporation into a lubricating oil base for the purpose of increasing its film-rupture strength. However, although many of the compounds suggested are effective to this end, there arises the disadvantage that the blended oil has a corrosive efiect upon ,the metalsurfaces in contact with it. This disadvantage presents a serious problem which is of particular importance in modern aircraft engines employing high duty bearing materials of the composite metal type (such as cadmiumnickel bearings) which are especially susceptible to corrosive attack. A further important disadvantage of known compounds added to the lubrieating oil base is that the'improvements which they impart diminish with increase in temperature and may afford little or no advantage under operating conditions at high' temperature. A typical class of known additives which suffer from the foregoing disadvantages are the organic compounds "of phosphorus, for example, organic phosphites and phosphates.

Ihave conducted an extensive investigation on the problem and have now found that the filmrupture strength of a lubricating oil base can be considerably increased and its corrosive effect upon composite metal bearings substantially decreased by the inclusion therein ofa small proportion of a mixture comprising an organic compound containing trivalent phosphorus (in the 'form for example of a phosphite radical) and an oil-soluble organic metallic compound with or without an organic compound containing a phosphate radical, and that the "extreme pressure" properties of the blended lubricating composition thus obtained are still manifested at high temperature. I have also found that said organic compound containing trivalent phosphorus may be replaced by organic phosphate and that useful properties are still retained.

The surprising fact is that the film-rupture strength of these blended lubricating compositions is markedly superior to that which is imparted to the lubricating oil base byany one of the specified ingredients of said mixture, employed singly Particularly striking is the effect of the conjoint use of the three ingredients of the mixture above specified.

.Accordingto the present invention, therefore a lubricating composition especially a lubricating composition which is to carry high bearing loads at high temperatures, comprises a lubricating oil. base in which there is dispersed a small proportion of an oil-soluble organic metallic compound,

and either or both of an organic compound containing trivalent phosphorus and an organic com-- pound containing a phosphate radical.

The organic compound containing trivalent phosphorus may be for example, a simple aryl or alkyl phosphite, a mixed phosphite or a long chain compound in which a phosphite radical occurs more than once in the molecule. Examples of suitable phosphites are tributyl phosphite and triamyl phosphite. Likewise the organic compound containing a phosphate radical may be a simple aryl or alkyl phosphate or a mixed phosphate. Examples of suitable phosphates are tricresyl phosphate, triphenyl phosphate and trinaphthyl phosphate.

The oil-soluble organic metallic compound employed is preferably a heavy metal soap but other oil-soluble organic metallic compounds may be used. Preferably, oil-soluble organic compounds of tin are employed. At present, tin oleate is the preferred material-but such compounds as tin phenyl might be used with advantage.

A preferred embodiment of the present invention comprises a mineral 011 base in which there is dispersed a small proportion each of tributyl phosphite, tricresyl phosphate and tin oleate.

The amount of the addition agents which, in accordance with the present invention, are incorporated in the lubricating oil base is but small- In'general, amounts up to 10% by weight of the lubricating oil base are suflicient.. Good results are usually obtained with a total amount of the three ingredients of the order of 1% to 2% by weight.

The proportions in which the individual additives may be present can be varied. In this connection, regard must be had to the particular lubricating oil base which is to be used. With lubrieating oils having but little corrosive attack upon the metal surfaces to be lubricated, the propor-v tion of phosphite may be small in comparison with the amount of phosphate used (this is'an' advantage because many phosphates are both readily available and cheap), or may be omitted.

The invention is'illustrated by the following non-limitative example.

Example A solvent-refined c lubricating 011 base was compounded with a mixture comprising 0.5% oitricresyl phosphate, 0.10% or tributyl phosphite and 0.10% of tin oleate. Tests were conducted to compare the corrosive effect and film-rupture strength of the blended oil with the corresponding properties of:

(a) The lubricating oil base alone (b) The oil base containing 0.5% tricresyl phosphate (c) The oil base containing 0.10% tributyl phosphite (d) The oil base containing 0.10% tin oleate.

In the corrosion tests, the corrosive eil'ect on a nickel-cadmium bearing alloy at 170 C. was observed, the extent of corrosion being measured by determining the loss inweight of the bearing alloy after 50 hours exposure. It was found that the plain oil had a marked corrosive action, a loss in weight of over 500 milligrams being recorded, the oil containing 0.5% tricresyl phosphate and the oil containing 0.1% tin oleate were similarly markedly corrosive while the oil containing 0.1% tributyl phosphite and that containing the three ingredients as above specified were practically non-corrosive, giving after 100 hours of contact with the alloy, an alloy loss in weight of not more than 30 milligrams.

The film-rupture strength of the various specimens was compared in a testing apparatus of conventional type in which means .were provided for controlling the temperature of the lubricant rubbing surfaces. The results were as follows:

It will be observed that the specimen containing all three additives in accordance with the foregoing example, is surprisingly superior in film-rupture strength over the other specimens tested, more especially at high temperature. It can, furthermore, .be shown that a comparable strength is not obtained by the use of a phosphite, a phosphate 01 a metal soap used singly as an additive.

In a practical test on the lubrication of the reduction gearing of an internal-combustion engine under conditions of high stress it was found that whereas the film-rupture strength of a normal lubricant was insufilcient to prevent damage to the teeth of the gear as for example by excessive wear, a lubricant made in accordance with the present invention was found to be effective in preventing such damage to the teeth under similar operating conditions.

Lubricating compositions of the present invention exhibit the added advantages of a marked degree or resistance to oxidation and to the tormation or carbonaceous and gummy deposits at high operating temperatures.

1 claim:

1. A lubricating composition substantially noncorrosive to bearing materials of the composite metal type including cadmium-nickel bearin materials even at temperatures or the order of 170 C. and having high film-rupture strength at such temperatures, which composition comprises, a lubricating oil base having incorporated therein, 0.5% tricresyl phosphate, 0.1% tributyl phosphite and 0.1% tin oleate, all by weight based on the weight of said lubricating oil base.

2. A lubricating composition substantially noncorrosive to bearing materials of the composite metal type including cadmium-nicke1 bearing materials even at temperatures of theorder of 170 C. and having high film-rupture strength at such temperatures, which composition comprises, a lubricating oil base having incorporated therein as addition materials, at least 0.1% tin oleate, at least 0.5% of phosphate'selected from the group consisting of tricresyl phosphate, triphenyl the lubricating oil base, the total amount of said addition materials being not greater than 10%.

3. A lubricating composition substantially noncorrosive to bearing materials of the composite metal type, including cadmium-nickel bearing materials even at temperatures of the order of C. and having high film-rupture strength at suchtemperatures, which composition comprises, a lubricating oil base having incorporated therein as addition materials, at least 0.1% tin oleate, at least 0.5% of tricresyl phosphate and at least 0.1% of tributyl phosphite, all by weight based on the weight of said lubricating 011 .base, the total amount of said addition materials being not greater than 10%.

4. A lubricating composition substantially noncorrosive to bearing materials of the composite metal type including cadmium-nickel bearing materials even at temperatures of the order of 170 C. and having high film-rupture strength at such temperatures, which composition comprises, a lubricating oil base having incorporated therein, 0.1% tin oleate, 0.5% of a phosphate selected from the group consisting of tricresyl phosphate, triphenyl phosphate and trinaphthyl phosphate and 0.1% of a phosphite selected from the group consisting of tributyl phosphite and triamyl phosphite, all by weight based on the weight of said lubricating oil base.

WILLIAM HELMORE. 

